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Discussion Starter · #1 · (Edited)
Techno question here... in trying to understand BB height:

Lower BB = better cornering plus more pedal strikes. Got that.
And BBs for 6" inch bikes are debated here between 14.5 and 13.5. Got that as well.
But what's really important - the BB height itself or how it relates to the wheelbase?

My 2008 large RFX has a 14.25" BB with a 160mm fork and Minion 2.3 tires, and a 45" wheelbase. The medium RFX has a 44.1" wheelbase - so wouldn't my current ride have a similar feel to a medium RFX if it had just under 14" BB ?

(Emm... from previous experience... sincere question here in trying to assess future bikes - so wisecrack somewhere else please... ;))
 

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tald said:
Techno question here... in trying to understand BB height:

Lower BB = better cornering plus more pedal strikes. Got that.
And BBs for 6" inch bikes are debated here between 14.5 and 13.5. Got that as well.
But what's really important - the BB height itself or how it relates to the wheelbase?

My 2008 large RFX has a 14.25" BB with a 160mm fork and Minion 2.3 tires, and a 45" wheelbase. The medium RFX has a 44.1" wheelbase - so wouldn't my current ride have a similar feel to a medium RFX if it had just under 14" BB ?

(Emm... from previous experience... sincere question here in trying to assess future bikes - so wisecrack somewhere else please... ;))
Hmmm. I had never thought of it that way, but I suppose you are correct. It certainly makes sense that these two dimensions would factor into center of gravity and spreading out the center of mass. I would think based on my limited math skills that while compromising some agility, having a longer wheelbase and higher center of gravity would be a lot more forgiving and comfortable than a shorter BB and shorter wheelbase, while cornering should stay pretty much the same....(and possibly more cockpit setup options).. RCC has an 08 RFX just just feels fantastic in the cockpit. He's running a 180mm fork and while I haven't "really" ridden it, it appears to be just as capable (if not more so than my 06 RFX with a 180mm (both mediums). Could that be to the longer wheelbase? Then again the beefier 06 is more "purpose" driven. I think I just convinced myself that I need an 07-08 RFX to compliment my HL. Damn you!:p
 

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I don't know but it make sense. My med RFX also is at 14.25" BB height with a 7.75x2.25 shock, rest of the specs similar to yours. I'm surprised your BB is that low, I think it may be in the tires? I think this bike corners and rides great. I have an friend with a large, may have to do a little comparing.
 

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victim said:
I don't know but it make sense. My med RFX also is at 14.25" BB height with a 7.75x2.25 shock, rest of the specs similar to yours. I'm surprised your BB is that low, I think it may be in the tires? I think this bike corners and rides great. I have an friend with a large, may have to do a little comparing.
Have you tried lowering the stack and going with a taller riser? It's MY experience is that having the "meat" of the bar as close the wheel as possible helps considerably with tracking on the downs... as well as more maneuverable on the climbs. Gives you a bit of leverage to muscle the fork into into more "sag".

Sweet bike..wannna trade?:D
 

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I did try that, but they didn't have the width of the sunlines (27.5 vs 29) so they didn't feel as good, so I guess it wasn't a fair test. I just may try that out and put this bar on my 5 spot. Not accepting trades at the moment, thanks for the compliment though.

In all seriousness the bike is great as is but in true homer fashion I would like to try it with just a little less BB height and see how that would be. I'm curious about the correct answer to Tald's question?
 

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victim said:
I did try that, but they didn't have the width of the sunlines (27.5 vs 29) so they didn't feel as good, so I guess it wasn't a fair test. I just may try that out and put this bar on my 5 spot. Not accepting trades at the moment, thanks for the compliment though.

In all seriousness the bike is great as is but in true homer fashion I would like to try it with just a little less BB height and see how that would be. I'm curious about the correct answer to Tald's question?
Too bad the next gen TNT RFX got sidestepped for the DW. I think it could have been a killer!
 

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Along the lines of the OP's original question, I have often thought about the handling of large v. medium frames.

It seems that most frames are designed around the medium size. Then the small and large are "made to fit". Do you think the handling characteristics of bikes in the small, large, and XL sizes differ from the medium (or primary designed size)?

The reason I ask is because I rode a large 6 pack for a couple years. For the most part I really liked the bike, but there were a couple things that kept me looking for other bikes. After I sold it I rode my buddies medium 6 pack a bunch of times and loved it. I am 6'1" and on paper the medium should be too small. The medium is a little bit cramped, but it climbs and descends great and I prefer it over the large i used to have.

Besides never looking as good as the mediums, do the large frames differ in handling from mediums?

I know it would be too expensive, but it seems like different sized frames should have different length chain stays.

TG
 

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Discussion Starter · #8 · (Edited)
G-Air, my original question indeed comes from the belief that the medium sized frame is the most popular, most tested, most reviewed, most engineered variant. I don't know if that's correct or not.

As a comparison, The medium Intense Tracer at 6" travel has a 67.5deg headangle , a low BB - 13.8", but also a short wheelbase - 43.5". That's the same headangle with just a bit HIGHER BB-to-wheelbase ratio than the Large RFX! So should I treat the Intense as a low bike better for attacking vs the RFX? Or is it just the opposite?

Victim - if you're running clipless then throw on a pair of flats - that will move you down around 1 cm. And yes it does make a difference.
Edit: just now looked at the snowy flats you're already running in the image posted above. Dahh...
 

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G-AIR said:
king as good as the mediums, do the large frames differ in handling from mediums?

I know it would be too expensive, but it seems like different sized frames should have different length chain stays.

TG
Yep! +1
 

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I've always felt that it's the ratio of BB height to wheelbase that gives you the "feel" of if the bike is low or not. I've sat back and watched people go absolutely crazy for slacked out bikes like the SX trail that aren't really low. When you ask about low-BB bikes, people start listing the bikes that felt low to them, and usually many, if not most of the suggestions actually do not have a low BB at all. So longer wheelbase with the "same" BB as a shorter wheelbase affects how low it feels to me. It also means that with the longer wheelbase bike you can still feel like you are "in" the bike rather than sitting way up on top of it, even though the BB isn't really all that low.

That's just been what I've felt over the years.
 
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